Gas field ionization ion source and ion beam device

ABSTRACT

Provided is a gas field ionization ion source capable of emitting heavy ions with high brightness which are suitable for processing a sample. The gas field ionization ion source according to the present invention includes a temperature controller individually controlling the temperature of the tip end of an emitter electrode ( 1 ) and the temperature of a gas injection port part ( 3 ) of a gas supply unit.

TECHNICAL FIELD

The present invention relates to a gas field ionization ion source andan ion beam device including the same.

BACKGROUND ART

Non-patent Document 1 listed below describes focused ion beam(abbreviated as FIB) devices each of which includes a gas fieldionization ion source (abbreviated as GFIS) and uses gas ions ofhydrogen (H₂), helium (He), neon (Ne), or the like. Such gas FIB deviceshave an advantage of not contaminating samples with Ga unlike gallium(Ga: metal) FIB devices including liquid metal ion sources (abbreviatedas LMISs) which are commonly used currently. In Non-patent Document 1,GFISs can form beams finer than Ga-FIB devices because gas ionsextracted from the GFISs have narrow energy width and the ion generationsource is small.

Non-patent Documents 2 and 3 and Patent Document 1 listed below disclosethat provision of a microprotrusion (emitter tip) to the tip end of theemitter of a GFIS or reduction of the number of atoms at the tip end ofthe emitter to a few atoms provides improvements in characteristics ofthe ion source, such as an increase in angular current density of theion source. As an example of fabrication of such a microprotrusion,Patent Documents 2 and 3 disclose fabrication from tungsten (W) of theemitter material by field evaporation. Non-patent Document 3 listedbelow discloses fabrication of the microprotrusion using a second metaldifferent from the emitter material of a first metal.

Non-patent Document 2 and Patent Documents 2 and 3 listed below disclosescanning charged particle microscopes including GFISs configured to emitions of He as a light element. From the viewpoint of weight ofirradiation particles, a He ion is about 7,000 times as heavy as anelectron but is light having a weight of about 1/17 of a Ga ion.Accordingly, sample damage depending on the magnitude of momentumtransferred to atoms of the sample from the irradiating He ions is alittle larger than that of electrons but is very smaller than that of Gaions. Moreover, the region where secondary electrons are excited bypenetration of the irradiating particles into the sample surface is morelocalized in the sample surface than that in the case of electronirradiation. Accordingly, it is expected that images by the scanning ionmicroscope (abbreviated as SIM) are more sensitive to information of thesample surface than images by scanning electron microscopes (abbreviatedas SEM). Furthermore, from the viewpoint of microscopes, the effect ofdiffraction in convergence of an ion beam can be ignored since ions areheavier than electrons. Accordingly, the SIMs are characterized byproviding an image with a very large depth of focus.

Non-patent Document 3 listed below states that an ion current can beincreased by decreasing the temperature of the emitter tip in the GFIS.Non-patent Document 3 also states that even if the temperature isdecreased lower than around the devaporization point (boiling point) ofthe gas, the ion current is not increased, but on the contrary reducedin some cases.

Patent Document 3 listed below states that the GFIS uses a gas mixture.The component ratio of the added gas is very low, and the purpose of theadded gas is not clear. According to the description of thespecification thereof, it can be thought that the added gas is expectedto contribute to formation or reproduction of the tip end of the emittertip or contribute to stabilization of the ion source. Moreover, the samedocument states that the GFIS includes plural independent gas supplymeans.

Patent Document 4 listed below states that first and second gases aretaken into an emitter region for generation of ion beams of the firstand second gases.

Patent Document 5 listed below describes an ion source including two ormore gas introduction lines in order to switch between a gas ion beamtype for processing of a sample and a gas ion beam type for observationof the sample.

PRIOR ART DOCUMENTS Patent Documents

-   Patent Document 1: Japanese Patent Laid-open Publication No.    58-854242-   Patent Document 2: Japanese Patent Laid-open Publication No.    7-192669-   Patent Document 3: Japanese Translation of PCT international    Application Publication No. 2009-517846-   Patent Document 4: Japanese Patent Laid-open Publication No.    2009-187950-   Patent Document 5: Japanese Patent Laid-open Publication No.    2008-270039

Non-Patent Document

-   Non-patent Document 1: K. Edinger, V. Yun, J. Meingailis, J. Orloff,    and G. Magera, J. Vac. Sci. Technol. B 15 (No. 6) (1997) 2365-   Non-patent Document 2: J. Morgan, J. Notte, R. Hill, and B. Ward,    Microscopy Today, Jul. 14, 2006) 24-   Non-patent Document 3: H.-S. Kuo, I.-S. Hwang, T.-Y. Fu, Y.-H. Lu,    C.-Y. Lin, and T. T. Tsong, Appl. Phys. Letters 92(2008) 063106

SUMMARY OF THE INVENTION

In the case of using a GFIS for processing a sample as in the case withGa-FIBs, it is possible to use a gas generating heavy ionic species witha high sputtering rate such as argon (Ar), for example. However, sincesuch a heavy gas generally has a high devaporization point (boilingpoint), the temperature of the gas needs to be increased sufficiently,which leads to an increase in the temperature of the emitter tip. Thismakes it difficult to obtain enough ion current, so that it is difficultto provide an ion beam with high brightness.

The present invention was made to solve the aforementioned problems, andan object of the present invention is to provide a GFIS capable ofemitting heavy ions with high brightness which are suitable forprocessing a sample.

A gas field ionization ion source according to the present inventionincludes a temperature controller individually controlling a temperatureof the tip end of an emitter electrode and a temperature of a gasinjection port of a gas supply unit.

According to the gas field ionization ion source of the presentinvention, the temperature of the tip of the emitter electrode can bedecreased with the gas kept at high temperature. Accordingly, thetemperature of the tip end of the emitter electrode can be decreased inorder to obtain an ion beam with high brightness while the temperatureof the gas is increased in order to emit heavy ions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing a configuration of an ion beamdevice 200 according to Embodiment 1.

FIG. 2 is a view illustrating an internal configuration of an extractionvoltage application unit 4.

FIG. 3 is a cross-sectional view showing a configuration with a gasinjection port part 3 of a gas supply pipe 30 modified.

FIG. 4 is a schematic view showing a configuration of an ion beam device200 according to Embodiment 2.

FIG. 5 is a cross-sectional view showing a configuration of an ion beamdevice 200 according to Embodiment 3.

FIGS. 6A and 6B are views showing a change of an ion beam in the case ofincreasing the extraction voltage.

FIG. 7 is a view showing an internal configuration of an extractionvoltage applying unit 4-2 of Embodiment 3.

FIG. 8 is a schematic view showing a configuration of an ion beam device200 according to Embodiment 4.

FIGS. 9A to 9D are views showing configuration examples of GFISsexerting equivalent effects to Embodiments 1 to 5.

MODES FOR CARRYING OUT THE INVENTION Embodiment 1

FIG. 1 is a cross-sectional view showing a configuration of an ion beamdevice 200 according to Embodiment 1. The ion beam device 200 includes agas field ionization ion source (GFIS) and converging an ion beamemitted from the GFIS to irradiate a sample with the ion beam forobservation or processing of the sample. Hereinafter, a description isgiven of constituent components shown in FIG. 1.

A vacuum vessel 10 is kept at ultrahigh vacuum of the 10⁻⁸ Pa range byan vacuum pumping system (not shown) connected to an exhaust port 11. Ifthe ion beam device 200 is not connected to another device, the vacuumvessel 10 is closed by a valve 12.

In the vacuum vessel 10, an emitter tip 1 having a needle-like point andan extraction electrode 2 having an opening facing the tip end of theemitter tip 1 are placed. The emitter tip 1 requires an axis alignmentmechanism but is not shown in the drawings to simplify the description.

A gas injection port part 3 of a gas supply pipe 30 supplies gas to beionized to near the tip end of the emitter tip 1. The gas supply pipe 30is connected to a gas cylinder 31 through a valve 32.

The emitter tip 1 and the extraction electrode 2 are connected to anextraction voltage application unit 4 through high voltage introductionterminals 40-1 and 40-2, respectively. Ionization needs only one linefor the purpose of applying an electrical potential to the emitter tip1. In Embodiment 1, two lines are connected to the emitter tip 1 for thepurpose of heating a filament unit at the base of the emitter tip 1.

The emitter tip 1 is cooled by heat exchange with a cooing head 20introduced from the outside of the vacuum vessel 10 (the cooling head 20is connected to a Gifford-McMahon freezer, for example) through a heattransfer braided cable (oxygen-free copper) 21-1, a heat transfersupporter (oxygen-free copper) 22-1, and a heat transfer insulator(sapphire) 23-1. The gas injection port part 3 is cooled by heatexchange with the cooling head 20 through a heat transfer braided cable(oxygen-free copper) 21-2 and a heat transfer supporter (oxygen-freecopper) 22-2. The gas injection port part 3 is made of oxygen-freecopper having good heat conductivity. Since such materials have goodheat conductivities, the emitter tip 1 and gas injection port part 3 arecooled to substantially a same temperature.

The heater 25 heats the gas injection port part 3. The temperature ofthe gas injection port part 3 can be therefore set higher than theemitter tip 1. Even in the case of using gas with a high devapolizationpoint, therefore, the temperature of the gas can be kept at thedevapolization point or higher.

The aforementioned materials of oxygen-free copper are plated with goldin order to reduce heat radiation. Heat insulation supporters (stainlesssteel thin-wall pipes) 24-1 and 24-3 contribute to blocking entry ofheat from the outside. Moreover, the gas supply pipe 30 is made ofstainless steel having poor heat conductivity other than the gasinjection port part 3 and is wound to be extended to a long conductiondistance, thus preventing heat from entering from the outside. Moreover,in order to keep the temperature of each unit stable, several heatshield walls are required but are not shown in the drawings forsimplification.

FIG. 2 is a view showing an internal configuration of the extractionvoltage application unit 4. An acceleration voltage controller 43 and anextraction voltage controller 44 respectively control high voltage powersupplies 41-1 and 41-2 while adjusting the subordinate-superior relationbetween acceleration voltage Va and extraction voltage Vex so that theapplied voltage does not become negative.

An emitter tip heating power supply 42 is configured to heat the emittertip 1 to about 1000 K to improve the condition of the point thereof andis not used for emitting ions.

A “temperature controller” in Embodiment 1 includes the mechanisms foradjusting the temperatures of the emitter tip 1 and gas supply port 3such as the cooling head 20, heat transfer braided cables, heat transfersupporters, heat transfer insulators, and heater 25. The emitter tipheating power supply 42 is not included in the temperature controller inEmbodiment 1.

A “gas field ionization ion source” according to Embodiment 1 includesthe emitter tip 1, extraction electrode 2, gas supply pipe 30, gasinjection port part 3, extraction voltage application unit 4, and theaforementioned temperature controller.

Hereinabove, the description is given of the configuration of the ionbeam device 200 according to Embodiment 1. Next, a description is givenof the operation of the ion beam device 200 according to Embodiment 1.

As the extraction voltage application unit 4 applies a voltage with theemitter tip set positive and the extraction electrode negative, some ofgas atoms (molecules in some cases) going out from the gas injectionport part 3 and reaching the tip end of the emitter tip 1 becomepositive ions due to field ionization, thus causing ion emission at acertain tip end of time.

In conventional ion beam devices, for the purpose of increasing gaspressure around the tip end of the emitter tip 1, a substantially closedchamber is provided ahead of the gas injection port part 3, or the gasinjection port part 3 and emitter tip 1 are cooled with a samerefrigerant. Such configurations result in that the gas injection portpart 3 and emitter tip 1 are set to substantially a same temperature.

Accordingly, if the emitter tip 1 is cooled to increase emitted ions,gas is also cooled. As the temperature of the gas approaches thedevapolization point (boiling point), the gas is gradually liquefied,and supply of the gas can be inhibited. This can be thought to preventan enough increase in ions emitted by field ionization from heavy gashaving a high devaporization point.

In Embodiment 1, therefore, a cooling system is configured so that thegas injection port part 3 always has a temperature higher thantemperature of the emitter tip 1. By the operations of the cooling head20, heat transfer braided cables 21-1 and 21-2, heat transfer supporters22-1 and 22-2, and heat transfer insulator 23-1, the emitter tip 1 andgas injection port part 3 are cooled to increase the emitter current andallow emission of an ion beam with high brightness. Moreover, in orderto address the high devaporization point of heavy ions, the gasinjection port part 3 is heated with a heater 25 as needed. With suchconfigurations, the temperatures of the emitter tip 1 and the gasinjection port part 3 can be individually adjusted.

Hereinabove, the description is given of the operation of the ion beamdevice 200 according to Embodiment 1. The followings complement theother points.

In Embodiment 1, the emitter tip 1 is a hairpin-shaped filament to thetip end of which a single crystal of tungsten (W) is welded. On the(111) crystal plane of W at the tip end of the emitter tip 1, an atompyramid of iridium (Ir) is formed. The gas is Argon (Ar). The mass of anAr ion is a little larger than half the mass of a Ga ion, and Ar ionsare therefore suitable for processing.

The ion extraction voltage is about 4 kV. The gas injection port part 3is located several millimeters away from the emitter tip 1 to preventexcessive discharge. When the temperature of the emitter tip 1 isdecreased to about 40 K with the gas injection port part 3 being kept ata temperature of about 90 K (the boiling point of Ar is about 87 K), theion current monotonically increases.

As a result, the ion current of Ar, which had been said to have a peakat around 70 K, can be increased several times or more.

The ion beam device 200 can use xenon (Xe) gas, for example, which isheavier than Ar. In such a case, the temperature of the gas injectionport part 3 needs to be increased to about 170 K.

In Embodiment 1, only one GM freezer is used, but two independentfreezers may be used. Use of two independent freezers increases the costbut facilitates temperature control. A second GM freezer may be providedinstead of the heater 25 or together with the heater 25 to adjust thetemperature of the gas injection port part 3, for example.

In Embodiment 1, the extraction voltage application unit 4 has aconfiguration shown in FIG. 2 but may employ another configuration ifappropriate voltage difference can be generated between the emitter tip1 and extraction electrode 2.

FIG. 3 is a cross-sectional view showing a configuration with the gasinjection port part 3 of the gas supply pipe 30 modified. In FIG. 1, thegas injection port part 3 of the gas supply pipe 30 is protruded in anozzle-like shape. However, in the configuration shown in FIG. 3, theinjection port part 3 does not include the nozzle-like protrusion. Insuch a case, part around the opening (gas outlet) of the heat transfersupporter 22-2 is treated as a gas injection port part 3-1 of the gassupply pipe 30.

In this embodiment, as shown in FIGS. 1 and 3, it is desirable that theopenings of the gas injection port parts 3 and 3-1 of the gas supplypipe 30 are directed to the tip end of the emitter tip 1. This is forthe purpose of increasing the possibility that supplied gas directlyreaches the tip end of the emitter tip 1. Moreover, if the gas reachesthe supporting member at the base of the emitter tip 1 instead of thepoint thereof, the gas kept at the devaporization point (boiling point)or more is cooled and adsorbed. The gas therefore hardly reaches the tipend of the emitter tip 1.

However, since the gas is emitted and spread from the openings of thegas injection port parts 3 and 3-1, the direction of each opening has acertain allowance, and the openings do not need to be directed exactlyto the tip end of the emitter tip 1. Moreover, part of the gas notionized, most of which is exhausted, is likely to be adsorbed onto thesupporting member of the emitter tip 1 having a low temperature. It istherefore desirable that the gas adsorbed onto the supporting memberthereof is released by increasing the temperatures of the emitter tip 1and supporting member to the devaporization point (boiling point) of theused gas or higher. An emitter tip heating power supply 42 can be usedfor such heating.

As described above, according to Embodiment 1, the emitter tip 1 can becooled to increase the emitter current while the gas injection port part3 is heated by the heater 25 to be kept at the devaporization point orhigher. Accordingly, even in the case of using gas of heavy ions such asAr or Xe, it is possible to provide an ion beam having high brightnesswith the gas kept at the devaporization point or higher.

Embodiment 2

FIG. 4 is a schematic view showing a configuration of an ion beam device200 according to Embodiment 2 of the present invention. The ion beamdevice 200 according to Embodiment 2 is a device in which the GFISdescribed in Embodiment 1 (indicated by reference numeral 100 in FIG. 4)is incorporated in a focused ion beam device manufactured for aconventional Ga-LMIS. A description is given of each configuration ofFIG. 4 below.

An ion beam 5 emitted from the emitter tip 1 is converged byelectrostatic lenses 102-1 and 102-2 to irradiate the sample 6. Theirradiation position of the ion beam 5 on the sample 6 is adjusted bydeflecting the ion beam 5 with deflectors 103-1 and 103-2.

Secondary electrons 7 generated from the sample 6 are detected by asecondary electron detector 104, and a secondary electron observationimage in which signal intensity corresponds to the deflection intensityis formed by a display 110. The user can specify the position at whichthe ion beam 5 irradiates the sample on the screen while seeing thesecondary electron observation image using the display 110.

A lens system 102 including the electrostatic lenses 102-1 and 102-2, abeam limiting diaphragm 102-3, and an aligner 102-4 is controlled by alens system controller 105. A deflection system 103 including thedeflectors 103-1 and 103-2 is controlled by a deflection systemcontroller 106. Reference numerals of boxes indicating drivers for theunits thereof are omitted.

An “image processing unit” in Embodiment 2 corresponds to the display110. A “controller” corresponds to the lens system controller 105 anddeflection system controller 106.

As described above, according to Embodiment 2, it is possible to obtaina focused ion beam device using a beam of heavy ions such as Ar or Xefor processing of a sample.

Embodiment 3

Embodiment 1 and 2 describe that a heavy ionic species is emitted withhigh brightness. On the other hand, before processing, observation of anSIM image and the like is carried out in order to determine the beamirradiation position. In this process, it is necessary to project theion beam onto the sample. At this time, the ion beam can give extraprocessing damage to the sample. However, reducing the ion current ordose amount of ions for the purpose of reducing the processing damageincludes a problem.

First, the angle at which ions are emitted from the GFIS is about onedigit smaller than that in the case of the Ga-LMIS. Accordingly, even ifthe angle is limited, the ion current can be reduced only slightly.Moreover, if the SIM image is obtained with the dose amount of ionsreduced, the positional accuracy is reduced due to noise.

In Embodiment 3 of the present invention, in order to solve theaforementioned problems, a description is given of a configuration andan operation which allow use of beams of different ionic species betweenSIM image observation and processing by switching between differentionic species at high speed.

FIG. 5 is a cross-sectional view showing a configuration of the ion beamdevice 200 according to Embodiment 3. The ion beam device 200 accordingto Embodiment 3 includes a substantially same configuration as thatdescribed in any of Embodiments 1 and 2 but is different fromEmbodiments 1 and 2 in a configuration to switch between ionic species.

A gas cylinder 31-2 is filled with a gas mixture including plural majorcomponents.

An extraction limiting diaphragm 8 includes an aperture allowing passageof an ion beam emitted by the emitter electrode. By setting properposition and size of the aperture, the extraction limiting diaphragm 8selectively allows passage of a beam of a desired ionic species. Thedetails thereof are described with FIG. 6 later described.

An extraction voltage application unit 4-2 includes a memory configuredto store values of the extraction voltage according to the number ofmajor components of the gas mixture. These values are used to change theextraction voltage in response to the switch of the ionic species. Thedetails thereof are described with FIG. 6 later described. Theaforementioned memory included by the extraction voltage applicationunit 4-2 corresponds to a first storage in Embodiment 3.

Hereinabove, the configuration of the ion beam device 200 according toEmbodiment 3 is described. Next, a description is given of the operationof the ion beam device 200 according to Embodiment 3 in the case ofusing a gas mixture containing 40% He and 60% Xe.

FIGS. 6A and 6B are views showing a change of the ion beam with anincrease in extraction voltage. FIGS. 6A and 6B show an ion beam whenthe extraction voltage is high and when the extraction voltage is low,respectively.

Xe is more easily field ionized than He. Accordingly, as the extractionvoltage is increased, first, an ion beam 5-1 composed of only Xe ions asshown in FIG. 6A is emitted from the emitter tip 1, especially, from amicroprotrusion 1-1 at the tip end of the same.

As the extraction voltage is further increased, Xe starts to be emittedfrom a large area to reduce the brightness of the ion source, and thenthe ions are not emitted from the microprotrusion 1-1. The brightness ofthe ion source is further reduced.

As the extraction voltage is still further increased, He is also ionizedin addition to Xe. In this state, as shown in FIG. 6B, an ion beam 5-1composed of only He ions is emitted from the microprotrusion 1-1 at thetip end of the emitter tip 1. The ion beam 5-1 composed of only Xe ionsis emitted with a large angle from the periphery of the ion beam 5-2.

In the state of FIG. 6B, the spread angle of the ion beam 5-2 emittedfrom the microprotrusion 1-1 is not more than several degrees.Accordingly, the extraction limiting diaphragm 8 having an appropriateaperture selectively allows passage of the ion beam 5-2 composed of onlyHe ions out of He and Xe ions. In the example of FIG. 6, provision ofthe extraction limiting diaphragm 8 including an aperture not largerthan the spread angle of several degrees just under the emitter tip 1allows passage of the Xe ion beam when the extraction voltage is low andallows passage of the He ion beam when the extraction voltage is high.

As described above, the correspondence between values of the extractionvoltage in the states of FIGS. 6A and 6B and the ionic species used inthe same is previously stored in a storage device such as a memory.Accordingly, the ionic species (He and Xe ions herein) can be instantlyswitched from each other by calling the stored values of the extractionvoltage and changing the extraction voltage.

FIG. 7 is a view showing an internal configuration of the extractionvoltage application unit 4-2 in Embodiment 3. The configuration of theextraction voltage application unit 4-2 is substantially the same asthat described in Embodiment 1 using FIG. 2 but differs in that anextraction voltage controller 44-2 stores values of the extractionvoltage corresponding to the gas components in an extraction voltagememory 45 and can calls the same to change the extraction voltage.

Switch of the ionic species in the GFIS can be implemented by a methodof switching between plural gas cylinders 31 through a valve, forexample, instead of the method explained in Embodiment 3. However, ittakes several hours for gas to reach the stable state, and changing thegas is not real. Embodiment 3 is advantageous in that the ionic speciescan be switched from each other within a time required to change theextraction voltage (about several ms).

The method using the extraction limiting diaphragm 8 to selectivelyallowing the passage of a desired one of beams of plural kinds ofcomponents contained in the gas mixture can be used alone or can be usedin combination with the method explained in Embodiment 1 and 2.

In the case of a combination of Embodiment 3 and the method explained inEmbodiment 1 for using gas of heavy ions, the gas to be mixed inEmbodiment 2 can be gas of various types of heavy ions. In this case,the temperature of the gas injection port part 3 needs to be determinedaccording to the gas component having the highest boiling point in thegas mixture to be used. In the example shown in Embodiment 3, He has aboiling point higher than Xe, and the temperature of the gas injectionport part 3 should be set to, for example, about 170 K.

The gas mixture in Embodiment 3 includes two major components, but a gasmixture including three or more major components can be used in the sameway as that of Embodiment 3. Moreover, even in the case of using onlyionic species corresponding to two components in a gas mixture whichincludes three or more major components and storing only two values ofthe extraction voltage, the same effects as Embodiment 3 can be exerted.

Embodiment 4

FIG. 8 is a schematic view showing a configuration of an ion beam device200 according to Embodiment 4 of the present invention. The ion beamdevice 200 according to Embodiment 4 has a configuration in which theGFIS (indicated by reference numeral 100-2 of FIG. 8) explained inEmbodiment 3 is incorporated in a focused ion beam device manufacturedfor the conventional Ga-LMIS and is improved. Next, a description isgiven of the configuration of FIG. 8.

Provision of the GFIS 100-2 allows quick switch of the ionic speciesincluded in the gas mixture. To change the value of the extractionvoltage to be read, the ion extraction voltage application unit 4-2outputs a signal indicating a change of the extraction voltage to a lenssystem control 105-2 and a deflection system controller 106-2.

If the extraction voltage varies on the ionic species, the settings ofthe lens and deflection systems need to be changed. The lens systemcontroller 105-2 and deflection system controller 106-2 individuallyinclude storage devices such as memories storing the settings for eachionic species. Upon receiving the signal indicating the switch of theionic species from the ion extraction voltage application unit 4-2, thelens system controller 105-2 and deflection system controller 106-2 calla corresponding setting and perform a control corresponding to the ionicspecies. The memories included in the lens system controller 105-2 anddeflection system controller 106-2 correspond to a “second storage unit”in Embodiment 4.

The display 110-2 stores a secondary electron observation image in astorage device such as a memory. At this time, the display 110-2 storesthe signal from the ion extraction voltage application unit 4-2indicating the switch of the ionic species together as a label. Thecorrespondence between the ionic species and the secondary electronobservation images can be thus stored.

The advantages obtained by the aforementioned configuration aredescribed for the case of using a gas mixture of He and Xe.

The ion beam device 200 irradiates the sample 6 with the ion beam 5 ofHe ions to obtain a secondary electron observation image and then storesthe same in the storage device included in a display 110-2. Thereafter,the user visually confirms the secondary electron observation image onthe display 110-2 and specifies the position of a part to be processedon the secondary electron observation image. The ion beam 5 is changedto a Xe ion beam and is projected to the specified position forprocessing. In other words, to determine the irradiation position of theion beam, the ion beam device 200 irradiates the sample 6 with a He ionbeam, and at processing, the ion beam device 200 irradiates the sample 6with a beam of heavier Xe ions. In such manner, the ionic species can bechanged according to the purpose.

He ions hardly cause sputtering and therefore can provide a secondaryelectron observation image with a high SN ratio and a high resolution.The user determines the irradiation position while seeing thethus-obtained electron observation image and projects the Xe ion beam atthe determined position for processing. Accordingly, the ion beam device200 has an effect capable of processing the sample 6 with high accuracywithout damaging the same.

Embodiment 5

Embodiment 4 describes the configuration of the ion beam device 200capable of using different ionic species for determination of theirradiation position and for processing. In Embodiment 5 of the presentinvention, a description is given of an example in which the function ofswitching between the ionic species is used for another purpose.

In Embodiment 5, the gas supplied to the GFIS is a gas mixturecontaining 30% H₂ and 70% He. In this case, two types of secondaryelectron observation images by H and He are obtained for the same sample6. Since both of these ionic species hardly cause sputtering, it ispossible to obtain surface images with high SN ratios and highresolutions.

These two secondary electron observation images include componentshaving a same sensitivity to the surface roughness and components havingdifferent sensitivities to the surface element species. The display110-2 performs comparison calculation for these two secondary electronobservation images, thus generating an image specific to the surfaceroughness or an image specific to the surface element species, forexample.

On the other hand, if the secondary electron observation image isobtained using a single ionic species, the secondary electron yield(detection value/ion current) depending on variations in mass numbers ofelements/materials has a dependency on the element periodic low.Accordingly, the secondary electron yields for elements of differentmass numbers have very similar values in some cases. In such a case, itis difficult to discriminate the elements from each other in thesecondary electron observation image.

In contrast, if the ionic species is changed, the dependency of thesecondary electron yield depending on variations in mass numbers ofelements/materials on the element periodic low is changed. Accordingly,use of a combination of the secondary electron yields for differentionic species allows explicit determination of the difference betweenthe elements/materials. In this case, it is better to previously preparea table of second electron yields of both ionic species for eachelement/material. This can provide an effect facilitating identificationof elements/materials which are difficult to determine because havingsimilar detection values in the second electron observation imageobtained with a single ionic species. For example, the identificationcan be accurately carried out by providing a secondary electron yieldreference of a known material on a sample stage 101 and previouslycorrecting current of the ion beam 5 for both ionic species.

To obtain a more accurate observation image by comparing the processingresults using plural ionic species as described above is impossible byonly a secondary electron observation image obtained by a single ionicspecies.

In the above description, the secondary electron observation images arecompared. As for images obtained by detecting secondary particles otherthan secondary electrons, such as secondary ions or X rays, similar tothe secondary electron observation images, comparison calculation ofsecondary particle images obtained using different ionic speciespossibly provides new information on a sample.

Embodiment 6

Embodiments 3 to 5 show that ionic species can be changed quickly bycalling extraction voltages previously stored corresponding to the majorcomponents of a gas mixture from the storage device and calling thecorresponding settings of the lens and deflection systems.

It can be said that changing the extraction voltage according to theionic species is equivalent to changing the electrical field intensityat the tip end of the emitter tip 1 according to the ionic species.Accordingly, Embodiment 6 of the present invention describes aconfiguration capable of exerting an effect equivalent to changing theextraction voltage by changing the electric field intensity at the tipend of the emitter tip 1 through a method different from Embodiments 3to 5. Embodiment 6 also describes an operational example of such aconfiguration.

FIG. 9 illustrates views showing a configuration example of a GFISexerting an effect equivalent to that of Embodiments 3 to 5. Forsimplifying the drawings, FIG. 9 shows only an arrangement of theelectrodes and power supply.

FIG. 9A shows the same arrangement of the electrodes and power supply asthat of Embodiment 1. FIG. 9B shows another configuration exampleexerting an effect equivalent thereto.

In FIG. 9B, a suppression electrode 120 is provided between the emittertip 1 and extraction electrode 2. Between the emitter tip 1 andsuppression electrode 120, a suppression voltage application unit 121 isconnected. The suppression voltage application unit 121 applies asuppression voltage smaller than the extraction voltage to thesuppression electrode 120 to change the electrical field intensity atthe tip end of the emitter tip 1.

FIG. 9C shows the same arrangement of the electrodes and power supply asthose of Embodiments 3 to 5. FIG. 9D shows another configuration exampleexerting an effect equivalent thereto.

Changing the extraction voltage and ionic species in FIG. 9C isequivalent to changing the suppression voltage and ionic species in FIG.9D in which the suppression electrode 120 is provided.

The suppression voltage application unit 121-2 includes a storage devicestoring a suppression voltage value corresponding to a major componentof a gas mixture and has a function of calling the stored value andchanging the suppression voltage to the called value. To change theionic species, the suppression voltage application unit 12-2 calls thesuppression voltage value corresponding to the ionic species and appliesthe suppression voltage thereof to the suppression electrode 120. Theelectrical field intensity at the tip end of the emitter tip 1 can bethus changed according to the ionic species.

In the above description, the change of the electrical field intensityfor changing the ionic species is carried out only by changing thesuppression voltage. However, changing both the suppression voltage andextraction voltage to generate an equivalent change in voltage as awhole can also exert a similar effect.

Embodiment 7

The electrical field intensity at the tip end of the emitter tip 1 canbe changed using the suppression electrode 120 in the ion beam device200 described in FIG. 8 of Embodiment 4 as described in Embodiment 6.

In such a case, instead of the output of the ionic species switchingsignal from the extraction voltage application unit 4-2, the suppressionvoltage application unit 121-2 outputs a suppression voltage changesignal. Upon receiving the suppression voltage change signal, the lenssystem controller 105-2, deflection system controller 106-2, and display110-2 execute an operation according to the replacing ionic species.Embodiment 7 can therefore exert an effect equivalent to Embodiments 4and 5.

EXPLANATION OF REFERENCE NUMERALS

-   1: emitter tip, 1-1: microprotrusion, 2: extraction electrode, 3,    3-1: gas injection port part of gas supply pipe, 4, 4-2: extraction    voltage application unit, 5, 5-1, 5-2: ion beam, 6: sample, 7:    secondary electron, 8: extraction limiting diaphragm, 10: vacuum    vessel, 11: exhaust port, 12: valve, 20: cooling head, 21-1, 21-2:    heat transfer braided cable (oxygen-free copper), 22-1, 22-2: heat    transfer supporter (oxygen-free copper), 23-1, 23-3: heat transfer    insulator (sapphire), 24-1, 24-3: heat insulation supporter    (stainless steel thin-wall pipe), 25: heater, 30: gas supply pipe,    31, 31-2: gas cylinder, 32: valve, 40-1, 40-2: high voltage    introduction terminal, 41-1, 41-2: high voltage power supply, 42:    emitter tip heating power supply, 43: acceleration voltage    controller, 44, 44-2: extraction voltage controller, 45: extraction    voltage memory, 100, 100-2: gas field ionization ion source, 101:    sample stage, 102: lens system, 102-1, 102-2: electrostatic lens,    102-3: beam limiting diaphragm, 102-4: aligner, 103: deflection    system, 103-1, 103-2: deflector, 104: secondary electron detector,    105, 105-2: lens system controller, 106, 106-2: deflection system    controller, 110, 110-2: display, 120: suppression electrode, 121,    121-2: suppression voltage application unit

1. A gas field ionization ion source, comprising: an electrode unitincluding an emitter electrode and an extraction electrode; a gas supplyunit supplying a gas to near a tip end of the emitter electrode; avoltage application unit applying a voltage between the emitterelectrode and the extraction electrode to form an electrical field forionizing the gas; and a temperature controller individually controllinga temperature of the tip end of the emitter electrode and a temperatureof a gas injection port part of the gas supply unit.
 2. The gas fieldionization ion source according to claim 1, wherein the temperaturecontroller includes: a cooling unit simultaneously cooling the tip endof the emitter electrode and the gas injection port part of the gassupply unit; and a heating unit heating the gas injection port part ofthe gas supply unit.
 3. The gas field ionization ion source according toclaim 1, further comprising a suppression electrode provided between theemitter electrode and the extraction electrode, wherein the voltageapplication unit applies a suppression voltage between the suppressionelectrode and the emitter electrode to adjust an electrical field forionizing the gas.
 4. An ion beam device, comprising: a gas fieldionization ion source according to claim 1; a sample stage holding asample; a lens system converging an ion beam emitted from the gas fieldionization ion source and projecting the ion beam onto the sample; adeflection system deflecting the ion beam to change an irradiationposition of the ion beam on the sample; a secondary particle detectordetecting secondary particles emitted from the sample; an imageprocessing unit forming an observation image of the sample using aresult of detection by the secondary particle detector; and a controllercontrolling the lens system and the deflection system to adjust theirradiation position of the ion beam.
 5. The gas field ionization ionsource according to claim 1, wherein the gas supply unit is configuredto supply a gas mixture mainly containing gases of plural elements, andthe gas field ionization ion source further comprises: an extractionlimiting diaphragm having an aperture allowing passage of an ion beamemitted from the emitter electrode; and a first storage storing dataindicating a correspondence between a type of ions emitted from theemitter electrode and a voltage value applied by the voltage applicationunit during the emission.
 6. A gas field ionization ion source,comprising: an electrode unit including an emitter electrode and anextraction electrode; a gas supply unit supplying a gas mixture mainlycontaining gases of plural elements to near a tip end of the emitterelectrode; a voltage application unit applying a voltage between theemitter electrode and the extraction electrode to form an electricalfield for ionizing the gas; an extraction limiting diaphragm having anaperture allowing passage of an ion beam emitted from the emitterelectrode; and a first storage storing data indicating a correspondencebetween a type of ions emitted from the emitter electrode and a voltagevalue applied by the voltage application unit during the emission. 7.The gas field ionization ion source according to claim 6, furthercomprising a suppression electrode provided between the emitterelectrode and the extraction electrode, wherein the voltage applicationunit applies a suppression voltage between the suppression electrode andthe emitter electrode to adjust an electrical field for ionizing thegases.
 8. An ion beam device, comprising: the gas field ionization ionsource according to claim 5; a sample stage holding a sample; a lenssystem converging an ion beam emitted from the gas field ionization ionsource and projecting the ion beam onto the sample; a deflection systemdeflecting the ion beam to change an irradiation position of the ionbeam on the sample; a secondary particle detector detecting secondaryparticles emitted from the sample; an image processing unit forming anobservation image of the sample using a result of detection by thesecondary particle detector; and a controller controlling the lenssystem and the deflection system to adjust the irradiation position ofthe ion beam.
 9. An ion beam device, comprising: the gas fieldionization ion source according to claim 6; a sample stage holding asample; a lens system converging an ion beam emitted from the gas fieldionization ion source and projecting the ion beam onto the sample; adeflection system deflecting the ion beam to change an irradiationposition of the ion beam on the sample; a secondary particle detectordetecting secondary particles emitted from the sample; an imageprocessing unit forming an observation image of the sample using aresult of detection by the secondary particle detector; and a controllercontrolling the lens system and the deflection system to adjust theirradiation position of the ion beam.
 10. The ion beam device accordingto claim 8, further comprising a second storage storing data indicatinga correspondence between a type of ions emitted from the emitterelectrode and setting values of the lens system and the deflectionsystem, wherein the controller reads data corresponding to the datastored in the first storage from the second storage, and controls thelens system and the deflection system based on the setting valuesindicated by the read data.
 11. The ion beam device according to claim9, further comprising a second storage storing data indicating acorrespondence between a type of ions emitted from the emitter electrodeand setting values of the lens system and the deflection system, whereinthe controller reads data corresponding to the data stored in the firststorage from the second storage, and controls the lens system and thedeflection system based on the setting values indicated by the readdata.
 12. The ion beam device according to claim 8, wherein the imageprocessing unit receives an operation input to specify the irradiationposition of the ion beam, and the controller controls the deflectionsystem in a way to irradiate the specified irradiation position with theion beam.
 13. The ion beam device according to claim 9, wherein theimage processing unit receives an operation input to specify theirradiation position of the ion beam, and the controller controls thedeflection system in a way to irradiate the specified irradiationposition with the ion beam.
 14. The ion beam device according to claim8, wherein the image processing unit forms observation imagescorresponding to at least two species of ions emitted from the emitterelectrode, and performs correction processing using the observationimages to form and display a new secondary particle image.
 15. The ionbeam device according to claim 9, wherein the image processing unitforms observation images corresponding to at least two species of ionsemitted from the emitter electrode, and performs correction processingusing the observation images to form and display a new secondaryparticle image.